Menu

Discussion Forum

New Discussion
Filtrer

Note: This discussion is about an older version of the COMSOL Multiphysics® software. The information provided may be out of date.

Discussion Closed This discussion was created more than 6 months ago and has been closed. To start a new discussion with a link back to this one, click here.

Variable Frequency Microwave

Posted 5 juin 2014, 06:08 UTC−4 RF & Microwave Engineering, Materials, Modeling Tools & Definitions, Parameters, Variables, & Functions Version 4.3b 2 Replies

Silvernine
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Hello! I just started using COMSOL and I have been working on simulating a microwave wave guide with a dielectric material and been using a static frequency of 8.5 GHz and all my analysis related to that have been done. I now wanted to have an analysis to see the effect of a variable frequency wave generator upon a dielectric material. Basically instead of just putting 8.5 GHz through the wave guide, the microwave generator will put a microwave frequency that varies with time from 8.2 GHz to 12.4 GHz and then back again to 8.2 GHz. The problem is still a Frequency-Transient problem.

Initially I set my frequency (f0) as a parameter with the expression of 8.5[GHz]. I deleted that and instead created a new variable "f0". I also created a new parameter "t = 0[s]" so that COMSOL knows that "t" has been initiated. The new function was a triangle waveform "wv1". The expression for "f0" then becomes "10.3+(2.1*wv1(t[1/s]))[GHz]". However, it seems I'm missing something else as I keep getting an error:
Failed to find consistent initial values.
Last time step is not converged.

How should I proceed. I have read various threads and tried many different ways but I have not succeeded. Perhaps there is a smoother way of approaching this?

Thank you.
2 Replies Last Post 10 juin 2014, 17:17 UTC−4
Robert Koslover Certified Consultant
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago 7 juin 2014, 19:30 UTC−4
If all you want to do is explore different frequencies, don't introduce a time parameter at all. Just do a frequency domain problem and specify a range of frequencies. But if you truly must have an explicit time dependence, then you'll need to use the transient formulation, in which case you should specify a time-dependent waveform as your input. Note that such a waveform is technically an FM (frequency modulated) waveform. Look up frequency modulation at en.wikipedia.org/wiki/Frequency_modulation .
If all you want to do is explore different frequencies, don't introduce a time parameter at all. Just do a frequency domain problem and specify a range of frequencies. But if you truly must have an explicit time dependence, then you'll need to use the transient formulation, in which case you should specify a time-dependent waveform as your input. Note that such a waveform is technically an FM (frequency modulated) waveform. Look up frequency modulation at http://en.wikipedia.org/wiki/Frequency_modulation .
Silvernine
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago 10 juin 2014, 17:17 UTC−4
Thank you very much! That is a much better and simpler way than what I attempted.
Thank you very much! That is a much better and simpler way than what I attempted.

Note that while COMSOL employees may participate in the discussion forum, COMSOL® software users who are on-subscription should submit their questions via the Support Center for a more comprehensive response from the Technical Support team.

Suggested Content